Blender gets very slow to draw a scene having large number of plane?
Dupli objects
Try using Dupliverts (instances):

Create/import the point cloud as a mesh with only vertices:


Create a single tri by adding a plane (ShiftA&gt; Mesh &gt; Plane) and merging one edge with AltM:
 

Parent the tri to the point cloud by selecting both objects with the point cloud active (last selected) and pressing CtrlP.

With the point cloud active, enable Verts in Properties &gt; Object &gt; Duplication:


Add a track to constraint to the tri with the camera object as the target so that all the tris face the camera:



This has performed fine for me with point/vertex clouds of over 7000 vertices.
This will work with both BI and Cycles.
Halos
Another method for rendering point clouds is to use a Halo Material:

Create/Import a point cloud as vertex only mesh (no edges or faces):


Create a Halo material:



Note that this only works for BI.